"Recovery" is only an option for PV guest (not HVM), when you want to re-use the initial bootloader. It has nothing to do to recover anything else. You should be in HVM for all your VMs by the way, it's more secure and even faster.

@gskger thank you a lot. I'll try again.

@ninghe Are A and B identical servers? No shared storage? Does it work if you use normal snapshot mode?